Silicon carbide single-crystal substrate, silicon carbide epitaxial substrate and method of manufacturing them

Abstract

A silicon carbide single-crystal substrate includes a first main surface and a second main surface opposite to the first main surface. The first main surface has a maximum diameter of not less than 100 mm. The first main surface includes a first central region excluding a region within 3 mm from an outer circumference of the first main surface. When the first central region is divided into first square regions each having a side of 250 μm, each of the first square regions has an arithmetic average roughness (Sa) of less than 0.2 nm, and an oxygen concentration in each of the first square regions is not less than 5 atom % and less than 20 atom %.

The invention claimed is: 
     
       1. A silicon carbide single-crystal substrate including a first main surface and a second main surface opposite to the first main surface,
 the first main surface having a maximum diameter of not less than 100 mm, 
 the first main surface including a first central region excluding a region within 3 mm from an outer circumference of the first main surface, 
 when the first central region is divided into first square regions each having a side of 250 μm, each of the first square regions having an arithmetic average roughness (Sa) of less than 0.2 nm, and an oxygen concentration in each of the first square regions being not less than 5 atom % and less than 20 atom %. 
 
     
     
       2. The silicon carbide single-crystal substrate according to  claim 1 , wherein
 the second main surface includes a second central region excluding a region within 3 mm from an outer circumference of the second main surface, and 
 when the second central region is divided into second square regions each having a side of 250 μm, each of the second square regions has an arithmetic average roughness (Sa) of less than 0.2 nm. 
 
     
     
       3. The silicon carbide single-crystal substrate according to  claim 1 , wherein
 a mechanical polishing scratch is not formed on the first main surface. 
 
     
     
       4. A silicon carbide epitaxial substrate comprising:
 the silicon carbide single-crystal substrate according to  claim 1 ; and 
 a silicon carbide epitaxial layer provided on the second main surface of the silicon carbide single-crystal substrate, 
 each of the first square regions having an arithmetic average roughness (Sa) of less than 1.5 nm. 
 
     
     
       5. A method of manufacturing a silicon carbide single-crystal substrate, comprising the steps of:
 preparing a silicon carbide substrate including a first main surface and a second main surface opposite to the first main surface, by slicing a silicon carbide single crystal; and 
 removing a layer including a process-damaged layer formed on the first main surface side of the silicon carbide substrate, 
 after the process-damaged layer is removed, the first main surface including a first central region excluding a region within 3 mm from an outer circumference of the first main surface, 
 the method further comprising the step of measuring oxygen concentration in the first central region, 
 the first main surface having a maximum diameter of not less than 100 mm, 
 in the step of removing a layer including a process-damaged layer, not less than 1.5 μm of the layer including the process-damaged layer being removed, 
 when the first central region is divided into first square regions each having a side of 250 μm, an oxygen concentration in each of the first square regions being not less than 5 atom % and less than 20 atom %. 
 
     
     
       6. The method of manufacturing a silicon carbide single-crystal substrate according to  claim 5 , wherein
 each of the first square regions has an arithmetic average roughness (Sa) of less than 0.2 nm. 
 
     
     
       7. The method of manufacturing a silicon carbide single-crystal substrate according to  claim 5 , wherein
 the step of removing a layer including a process-damaged layer includes the step of performing chemical mechanical polishing on the first main surface. 
 
     
     
       8. The method of manufacturing a silicon carbide single-crystal substrate according to  claim 7 , wherein
 the step of performing chemical mechanical polishing on the first main surface includes the steps of
 performing first chemical mechanical polishing at a first polishing rate, and 
 after the step of performing first chemical mechanical polishing, performing second chemical mechanical polishing at a second polishing rate slower than the first polishing rate. 
 
 
     
     
       9. The method of manufacturing a silicon carbide single-crystal substrate according to  claim 5 , wherein
 the second main surface includes a second central region excluding a region within 3 mm from an outer circumference of the second main surface, and 
 when the second central region is divided into second square regions each having a side of 250 μm, each of the second square regions has an arithmetic average roughness (Sa) of less than 0.2 nm. 
 
     
     
       10. The method of manufacturing a silicon carbide single-crystal substrate according to  claim 5 , wherein
 a mechanical polishing scratch is not formed on the first main surface. 
 
     
     
       11. A method of manufacturing a silicon carbide epitaxial substrate, comprising the steps of:
 preparing a silicon carbide single-crystal substrate by the method of manufacturing a silicon carbide single-crystal substrate according to  claim 5 ; and 
 forming a silicon carbide epitaxial layer on the second main surface of the silicon carbide single-crystal substrate, 
 after the step of forming a silicon carbide epitaxial layer, each of the first square regions having an arithmetic average roughness (Sa) of less than 1.5 nm.